Fight Spam: ASSP (Anti-Spam SMTP Proxy) On CentOS 5.4

The Anti-Spam SMTP Proxy (ASSP) server project is an Open Source, Perl based, platform-independent transparent SMTP proxy server that leverages numerous methodologies and technologies to both rigidly and adaptively identify e-mail spam. ASSP is easy to set up because it requires only minor changes to the configuration of your your Mail Transfer Agent.

Also please read the ASSP documentation

Preliminary Note

In this tutorial I use a base 32 bit server install with the hostname server1.example.co.za with the IP address 10.0.0.10. These settings might differ for you, so you have to replace them where appropriate.

Adjust any package names if installing the EL4 or 64 bit packages. If any dependencies are unsatisfied, install the required packages and retry

If you have already installed the RPM Forge repository do so by running the following command

# rpm -Uhv http://apt.sw.be/redhat/el5/en/i386/rpmforge/RPMS/rpmforge-release-0.3.6-1.el5.rf.i386.rpm

Now lets install the Perl components needed to run ASSP (Anti-Spam SMTP Proxy) on CentOS 5.4. Firstly we upgrade Perl and then install the Perl modules.

# yum upgrade perl
# yum install perl-IO-Compress perl-Net-DNS perl-Email-Valid perl-File-ReadBackwards perl-Mail-SPF-Query perl-Mail-SRS perl-LDAP perl-MIME-tools perl-File-Scan-ClamAV

If and in order to run ClamAV anti-virus along with ASSP (Anti-Spam SMTP Proxy) install the ClamAV RPM

# yum install clamd
# chkconfig clamd on
# service clamd start

Next we’ll download and install ASSP (Anti-Spam SMTP Proxy)

Firstly check and grab the link for the latest version of ASSP on thier website, the version used in this post is ASSP Version: 1.6.5.5(1.0.02). Copy the direct download link for the latest version and download it.

Lets get ASSP.

# wget http://downloads.sourceforge.net/project/assp/ASSP%20Installation/ASSP%201.6.5.5/ASSP_1.6.5.5-Install.zip?use_mirror=ufpr

Make some preparations. Create the following directories that ASSP (Anti-Spam SMTP Proxy) will use to maintain the SPAM

# mkdir -p /usr/share/assp/spam
# mkdir /usr/share/assp/notspam
# mkdir /usr/share/assp/errors
# mkdir /usr/share/assp/errors/spam
# mkdir /usr/share/assp/errors/notspam

Now unpack ASSP.

# unzip ASSP_1.6.5.5-Install.zip
# cd ASSP_1.6.5.5-Install

And put ASSP in place.

# mv -f ASSP/* /usr/share/assp

Create following startup scripts.

# vi /etc/init.d/assp

#!/bin/bash
# 
# chkconfig: 2345 80 05
# Description: ASSP init.d script
# Hacked by : How2CentOS - http://www.how2centos.com

# Get function from functions library
. /etc/init.d/functions

# Start the service ASSP
start() {
        echo -n "Starting ASSP server: "
        cd /usr/share/assp
        perl assp.pl 2>&1 > /dev/null &
        ### Create the lock file ###
        touch /var/lock/subsys/ASSP
        success $"ASSP server startup"
        echo
}

# Restart the service ASSP
stop() {
        echo -n "Stopping ASSP server: "
        kill -9 `ps ax | grep "perl assp.pl" | grep -v grep | awk '{ print $1 }'`
        ### Now, delete the lock file ###
        rm -f /var/lock/subsys/ASSP
        success $"ASSP server shutdown"
        echo
}

### main logic ###
case "$1" in
  start)
        start
        ;;
  stop)
        stop
        ;;
  status)
        status ASSP
        ;;
  restart|reload|condrestart)
        stop
        start
        ;;
  *)
        echo $"Usage: $0 {start|stop|restart|reload|status}"
        exit 1
esac

exit 0

Lets start ASSP for the first time.

# cd /usr/share/assp
# perl assp.pl

You should be able to connect to ASSP web interface at this point. http://server1.example.co.za:55555. Specify anything for “username”, default “password” is nospam4me

At this point you shall see that ASSP is unable to bind to port 25. We need to stop and disable CentOS default mailer Sendmail.

# service sendmail stop
# chkconfig sendmail off

or

# yum remove sendmail

Now let’s shutdown ASSP with “Ctrl-C”. Now add the init script to chkconfig, set the run levels and start ASSP.

# chmod 755 /etc/init.d/assp
# chkconfig --add assp
# chkconfig assp on
# service assp start

Now lets do some minimal ASSP Configuration, point you browser to http://server1.example.co.za:55555

Network Setup

• SMTP Listen Port 25
• SMTP Destination 25

SMTP Session Limits
Testmode

• All Testmode ON – Running in this mode for two weeks to build the spamdb and whitelist

SPAM Control

• Prepend Spam Subject {ASSP-SPAM}

Copy Spam & Ham
Spam Lover/Hater
No Processing
Redlisting/Whitelisting
Relaying
Recipients
Validate Helo
Validate Sender
IP Blocking
Penalty Box
Delaying
SPF/SRS
DNSSBL
URIBL
Attachment Blocking
ClamAV

• Port or file socket for ClamAV (AvClamdPort) – /var/run/clamav/clamd.sock

Regex Filters / Spambomb
Bayesian Options
Backscatter Detection
Email Interface
File Paths
Collecting
Logging
LDAP Setup
DNS Setup
Server Setup

After a week rebuild the bayes database. Check the directories /usr/share/assp/spam and nospam for wrong entries, if good mail ends up in the spam directory please move it to the nospam directory and vice versa. After that do:

# cd /usr/share/assp
# perl rebuildspamdb.pl

Finally let’s add the bayes database rebuild to crontab.

# crontab -e

#       minute (0-59),
#       |       hour (0-23),
#       |       |       day of the month (1-31),
#       |       |       |       month of the year (1-12),
#       |       |       |       |       day of the week (0-6 with 0=Sunday).
#       |       |       |       |       |       commands
# -----------[ cron jobs  ]------------ #

# Weekly rebuild of the bayes database
    0     */2     *       *       *        cd /usr/share/assp && perl rebuildspamdb.pl